The existing Parents, Students, and Relationships Data Refresh routine can not be used to import Past Students.
The Data Refresh can not be used to Withdraw students nor to convert existing students to Alumni status.
If your school wants to import past students, we can import them and ensure they get the role = Past Student. However, what we cannot do is create their historical student enrollment records. Which means there would be no record of when (what school year, what grade, when they left) they attended.
If your school still wants to proceed, this request will be sent by Support to your Account Executive for a quote as it would be a billable event for a new DR.